Chapter 17 - 341 Chapter 17 17.1 a The slope coefficient...

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341 Chapter 17 17.1 a The slope coefficient tells us that for additional inch of father]s height the son&s height increases on average by .516. The y-intercept is meaningless. b On average the son will be shorter than his father. c On average the sons will be taller than his father. 17.2 a 2 1 ) , cov( x s y x b = = 43 . 16 87 . 7 = .479, x b y b 1 0 - = = 68.70 4 .479(67.14) = 36.54. (Excel: y± = 36.54 + .479x). b Nothing c For each additional inch of father&s height, the son&s height increases on average by .479 inch. 17.3 2 1 ) , cov( x s y x b = = 24 . 40 . 9 - = -39.17, x b y b 1 0 - = = 154.0 & (-.39.17)(8.2) = 475.19. (Excel: y& = 475.17 & 39.17x). The slope coefficient tells us that on average for each one-point increase in the mortgage rate the number of housing starts decreases by 39.17. 17.4 a 2x 1 s ) y , x cov( b = = 56 . 2 121 . = .047, x b y b 1 0 - = = 10.05 4 .047(3.47) = 9.89. (Excel: y& = 9.88 + .048x). b Nothing c The slope coefficient tells us that on average for each one-point increase in the inflation rate the return on common stocks increases by .048. 17.5 2 1 ) , cov( x s y x b = = 20 . 10 27 . 8 - = -.81, x b y b 1 0 - = = 67.28 ² (-.81)(8.18) = 73.91. (Excel: y| = 73.91 • .811x). The slope coefficient tells us that for each one-point increase in the amount of work marks decrease on average by .811. 342 17.6 a Scatter Diagram
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0 10 20 30 0 20 40 60 80 Length Test b 2 1 ) , cov( x s y x b = = 90 . 193 86 . 51 = .267, x b y b 1 0 - = = 13.80 4 .267(38.00) = 3.65. (Excel: y& = 3.64 + .267x). c 1 b = .267; for each additional second of commercial, the memory test score increases on average by .267. 0 b = 3.64 is the y-intercept. 17.7a 2 1 ) , cov( x s y x b = = 01 . 82 95 . 153 = 1.88, x b y b 1 0 - = = 74.06 41.88(27.95) = 21.51. (Excel: y& = 21.59 + 1.88x). b 1 b = 1.88; for each additional hour of study the final mark increases on average by 1.88. 0 b = 21.59 is the y-intercept. c The sign of the slope is logical. If the slope had been negative, it would indicate that on average the more one studied the lower the final mark would be. 17.8 a 2 1 ) , cov( x s y x b = = 90 . 3 08 . 3 = .790, x b y b 1 0 - = = 6.67 & .790(11.04) = -2.05. (Excel: y& = -2.03 + .788x). b 1 b = .788; for each additional year of education, Internet use increases on average by .788 hour. 0 b = -2.03 is the y-intercept. 17.9 a 2 1 ) , cov( x s y x b = = 11 . 55 44 . 6 - = -.117, x b y b 1 0 - = = 26.28 ¢ (-.117)(37.29) = 30.64. (Excel: y“ = 30.63 - .117x). b 1 b = -.117; for each additional year of age, the employment period decreases on average by .117. 0 b = 30.63 is the y-intercept.
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343 17.10 2 1 ) , cov( x s y x b = = 39 . 21 03 . 2 = .0949, x b y b 1 0 - = = 12.73 &.0949(34.61) = 9.45. (Excel: yK = 9.44 + .0949x). The appropriate compensation is 9.49 cents per degree API. 17.11a 2 1
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Chapter 17 - 341 Chapter 17 17.1 a The slope coefficient...

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